email address in To field changes to not proper email address when sent (outlook 2010 - exchange 2003)

We have a user on Windows 7 with Outlook 2010 sending an internal email.

We have noticed a strange occurrence that when he emails some internal members of staff the email address that is picked up from autocomplete / the GAL is not the proper address of the internal staff member he is emailing.

For example
If the users proper email address is
jonsmith @clientdomain.co.uk

When sending an email the received email shows
johnsmith@exmf024-nj-5.domain.local

How could this have happened?
Does this indicate there could be a problem.

Note that we had recently convert the users old NK2 file from Outlook 2003 and imported it to outlook 2010 (the user has recently upgraded his PC)

If anyone can give input please let us know. Note the network is Exchange 2003 and mostly Windows XP PC’s.

It sounds the email address is resolving to the internal address of the exchange server rather than external domain name and displaying that information. I would have the user send an email to an external email address and see what the reply to address is. If external email is replying to @clientdomain.co.uk and not @exmf024-nj-5.domain.local then I wouldn't think you have a real problem.

If I remember correctly on the Exchange Server there is a setting that will allow you select how you want internal and external email addresses to be displayed.

Though as long as internal external email is function smoothing, I don't think you have a real detrimental issue.

In exchange 2003 and outlook 2003 environment i have seen the same issue in FROM address
Majority of the time its a client end issue after upgrading of outlook 2003 to 2010
Please create a new outlook profile that will fix the issue

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